If that is all you want to know, then the first is wrong, the second is right.
If you want to know why the first is wrong and the second right, you will need to tell us why you thought they were correct.
I must be missing something - the first term is the interest - 0.05B/12 (monthly interest times principal). Mom puts in 240/6 = 40 a month, and Saleem takes out 50 a month, so that gives -10 for the other term. So isn't A correct?